Packet processing systems and methods

ABSTRACT

Packet processing system and method embodiments implemented in a peripheral component interconnect-express (PCIE) compliant system are disclosed. One method embodiment, among others, comprises receiving a packet having at least a first type of data and a second type of data over a PCIE connection, and segregating the entire packet into two contiguous groups, a first group comprising the first type of data and a second group comprising the second type of data.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to copending U.S. provisionalapplication entitled, “PACKET PROCESSING SYSTEMS AND METHODS,” havingSer. No. 60/726,533, filed Oct. 14, 2005, which is entirely incorporatedherein by reference.

TECHNICAL FIELD

The present invention is generally related to computer systems, and moreparticularly, is related to data transfer systems and methods incomputer systems.

BACKGROUND

Data transfer occurs between a central processing unit and memory andvarious other components in a computer system through a collection ofwires or an internal bus. Data transfer may also occur between internalcomponents and external devices through a bus, often referred to as anexpansion bus. Various standards have been created that specify themanner of data transfer over a bus. For instance, the peripheralcomponent interconnect (PCI) standard is a local bus standard developedby INTEL. A local bus comprises a data bus that may be connecteddirectly to a microprocessor. Another standard, referred to asPCI-Express (PCIE), is an input/output (I/O) interconnect bus standardthat comprises a defined protocol and architecture. The PCIE standardexpands upon the PCI standard, for instance, by doubling the datatransfer rates. PCIE specifies a 2-way serial connection that carriesdata in packets along two pairs of point-to-point data lanes (as opposedto the single parallel data bus of PCI). PCIE was developed to addressthe high data transfer speeds found in such high speed interconnects as1394b, USB 2.0, InfiniBand, and Gigabit Ethernet.

One challenge presented by PCIE is that of not allowing bytes to beskipped during write operations to various components (e.g., writes tomemory). For instance, some applications, such as stencil (s-data) anddepth (z-data) operations in graphics processing applications orcolor/alpha processing, may not require the entire packet body to beutilized. For instance, with regard to stencil and depth operations, thez-data occupies three of four bytes, s-data occupies one of the fourbytes, and computation of z-values may be the operation of interest (tothe exclusion of the s-data). Conventional approaches have fallen intotwo broad categories of solutions to this problem. One approach is toperform a read operation before the write, enabling a combined (merged)write that results in whatever was not intended to be written (e.g.,stencil byte) to simply be re-written as it was. However, one problemwith such a read and write approach is that such operations tend to beinefficient, which thus hampers performance.

Another approach is to segment the packet into manageable units toobtain the byte-enable features of the conventional PCI standard. Thatis, the conventional PCI standard includes provisions for byte-masks atthe head and tail portion of the packet (i.e., only a portion of theentire packet body). For example, for a 512-bit packet, the packet maybe segmented into eight transactions of 8 bytes each (e.g., four-bitmask at the header and four-bit mask at the tail). That is, thebyte-mask may be enabled for only head and tail portions of bytes foreach segment, allowing for selective write operations to be transacted.One downside of such an approach is that for each segmented packet aheader needs to be appended, which may result in poor performance due tothe passing of additional packet headers.

SUMMARY

Embodiments of the present disclosure provide systems and methods forprocessing packets in a peripheral component interconnect-express (PCIE)compliant environment. Such systems and methods receive one or morepackets of data. One packet may have one or more different types of datathat are not needed for a particular access request. For instance, in anexemplary graphics processing environment implemented using a PCIEprotocol, two different types of data, depth data (z-data) and stencildata (s-data), may be used. The depth data processing (z-data) mayrequire a read or write operation implemented on z data that is includedin a packet also having stencil data, which is not required for thisparticular write operation. Certain embodiments of the packet processingsystems disclosed herein segregate (separate) the z-data and stencildata into contiguous bytes of a first stencil data group and a secondz-data group. This grouping enables the packet processing system toselectively write one group to the exclusion of the other group.

Briefly described, in architecture, one embodiment comprises a packetprocessing system in a PCIE compliant system. Such a system comprises areceiver for receiving a packet having at least a first type of data anda second type of data over a PCIE connection, and a segregator forsegregating the entire packet into two contiguous groups, a first groupcomprising the first type of data and a second group comprising thesecond type of data.

The present disclosure also includes various method embodiments. Onemethod embodiment, among others, comprises receiving a packet having atleast a first type of data and a second type of data over a PCIEconnection, and segregating the entire packet into two contiguousgroups, a first group comprising the first type of data and a secondgroup comprising the second type of data.

Another embodiment comprises a graphics processor system. The graphicsprocessor system comprises a peripheral component interconnect-express(PCIE) connection, and a graphics processing unit coupled to the PCIEconnection, the graphics processing unit comprising packet logicconfigured to receive a packet having at least two types of data overthe PCIE connection and separate the entire packet into two contiguousgroups, a first group comprising a first type of data and a second groupcomprising a second type of data.

Other systems, methods, features, and advantages of the presentdisclosure will be or become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features, andadvantages be included within this description, be within the scope ofthe present invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosed systems and methods can be betterunderstood with reference to the following drawings. The components inthe drawings are not necessarily to scale, emphasis instead being placedupon clearly illustrating the principles of the disclosed systems andmethods. Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a block diagram of an exemplary graphics processor system,which serves as an exemplary environment in which embodiments of apacket processing system (and method) may be implemented.

FIG. 2A is a functional block diagram of select portions of embodimentsof the exemplary graphics processor system and packet processing systemshown in FIG. 1.

FIG. 2B is a functional block diagram that illustrates one embodiment ofa packet processing system as shown in FIG. 2A.

FIG. 3 shows an exemplary pre-packaged packet body structure andexemplary byte masks implemented by the packet processing system shownin FIG. 2B.

FIG. 4 shows an exemplary post-packaged packet body structure resultingfrom a mask and swap operation performed on the pre-packaged packetshown in FIG. 3.

FIG. 5 is a flow diagram that illustrates a packet processing methodembodiment.

DETAILED DESCRIPTION

Disclosed herein are various embodiments of packet processing systemsand methods. Such packet processing systems and methods employ a bytemask to an entire packet body (or equivalently, an entire packet) toenable select write and/or read operations to a circuit component, suchas memory. By employing a byte mask to the entire packet body,processing speeds and efficiencies are improved when compared toconventional systems. As previously described, conventional PCI systemscan apply a byte mask to the tail and head of a packet, but not to theentire body of the packet. Such conventional systems must break up apacket into manageable segments and append a header for each segment,resulting in poor performance due to increased processing time andstorage requirements due in part to the appended header. The packetprocessing systems and methods described herein obviate the need forsegmenting the packet body and appending headers to each segment or theneed for performing read and write operations as found in conventionalsystems. Thus, the packet processing systems and methods describedherein enable contiguous writes to a component.

Certain embodiments of the packet processing systems and methods aredescribed below in the context of a graphics processing environment thatincludes a graphics processing unit that generates triangles (or otherprimitives) and processes depth (z) data and stencil (s) data over aperipheral component interconnect express (PCIE) bus. However, oneskilled in the art would understand in light of the disclosure thatother bus communication protocols and standards may similarly fallwithin the scope of the disclosure. Further, although described in thecontext of write implementations, one skilled in the art wouldunderstand that read implementations would similarly benefit from theprinciples of the disclosed embodiments. Additionally, althoughdescribed in the context of stencil and depth data, others types of datamay similarly be used, such as the segregation and swapping of alphadata and color (e.g., RGB) data.

FIG. 1 is a block diagram of an exemplary graphics processor system 10,which serves as an exemplary environment in which embodiments of apacket processing system 100 (and method) may be implemented. In someimplementations, the graphics processor system 10 may be configured as acomputer system. The graphics processor system 10 may comprise a displaydevice 102 driven by a display interface unit (DIU) 104 and local memory106 (e.g., which may comprise a display buffer, texture buffer, commandbuffer, frame buffer, etc.). Local memory 106 may also be referred tointerchangeably herein as a frame buffer, storage unit, or simplymemory. Local memory 106 is coupled to a graphics processing unit (GPU)114 through a memory interface unit (MIU) 110. The MIU 110, GPU 114, andDIU 104 are coupled in one embodiment to a peripheral componentinterconnect express (PCIE) compatible bus interface unit (BIU) 118. Forinstance, one embodiment of the PCIE BIU 118 may be implemented using agraphics address remapping table (GART), although other memory mappingmechanisms may be employed. The BIU 118 and GPU 114 may becommunicatively coupled via a PCIE connection 103, over which dataand/or commands may be provided. In one embodiment, the BIU 118 and MIU110 are configured to send and receive data according to the PCIEprotocol and double data rate (DDR) memory protocol, respectively, as isknown.

The BIU 118 is coupled to a chipset 122 (e.g., north bridge chipset) orswitch. The chipset 122 comprises interface electronics to strengthensignals from a central processing unit (CPU) 126 (also referred toherein as a host processor) and to separate signals to and from a systemmemory 124 from those signals going to and from input/output (I/O)devices (not shown). Although a PCIE bus protocol is described, othermanners of connection and/or communication between the host processorand the GPU 114 may be implemented in some embodiments (e.g., PCI,proprietary high-speed bus, etc.). The system memory 124 also comprisesa graphics application (not shown) and driver software 150, whichcommunicates instructions or commands through the use of the CPU 126 toregisters in the GPU 114 and DIU 104. The driver software 150 orfunctionality of the same may be stored in system memory 124 andexecuted by the CPU 126. In one embodiment, the driver software 150provides compiled code (e.g., shader code) to the GPU 114 for executionin the GPU 114.

Additional graphics processing units may be employed in someembodiments, coupled for instance to the components shown in FIG. 1through the chipset 122 via a PCIE bus protocol. In one embodiment, thegraphics processor system 10 may be embodied in all of the componentsshown in FIG. 1, or fewer and/or different components than those shownin FIG. 1. Further, in some embodiments, additional components may beused, such as a south bridge chipset coupled to the chipset 122.

The packet processing systems 100 can be implemented in hardware,software, and/or firmware. When implemented in hardware (such as packet(P) units described below), the hardware can be implemented with any ora combination of the following technologies, which are all well known inthe art: a discrete logic circuit(s) having logic gates for implementinglogic functions upon data signals, an application specific integratedcircuit (ASIC) having appropriate combinational logic gates, aprogrammable gate array(s) (PGA), a field programmable gate array(FPGA), etc.

When implemented in software or firmware, such as the driver software150 controlling the hardware processing, such driver software 150 maycomprise an ordered listing of executable instructions for implementinglogical functions, can be embodied in any computer-readable medium foruse by or in connection with an instruction execution system, apparatus,or device, such as a computer-based system, processor-containing system,or other system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “computer-readable medium” can be anymeans that can contain, store, communicate, propagate, or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The computer readable medium can be, forexample but not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, device,or propagation medium. More specific examples (a nonexhaustive list) ofthe computer-readable medium would include the following: an electricalconnection (electronic) having one or more wires, a portable computerdiskette (magnetic), a random access memory (RAM) (electronic), aread-only memory (ROM) (electronic), an erasable programmable read-onlymemory (EPROM or Flash memory) (electronic), an optical fiber (optical),and a portable compact disc read-only memory (CDROM) (optical). Notethat the computer-readable medium could even be paper or anothersuitable medium upon which the program is printed, as the program can beelectronically captured, via for instance optical scanning of the paperor other medium, then compiled, interpreted or otherwise processed in asuitable manner if necessary, and then stored in a computer memory.

In addition, the scope of the certain embodiments of the presentinvention includes embodying the functionality of the preferredembodiments of the present invention in logic embodied in hardware orsoftware-configured mediums.

FIG. 2A is a functional block diagram of select portions of anembodiment of the GPU 114, including an embodiment of a packetprocessing system 100, designated as 100 a. The GPU 114 may include abuffer control initialization (BCI) unit 220, vertex shader (VS) 222,triangle setup unit (TSU) 224, span and tile generation (STG) unit 226,ZL1 unit 228, ZL1 cache 230, ZL2 unit 232, Z cache 234, P units 236 and238, pixel shader (PS) 240, texture (T) cache 242, ZL3 unit 244,destination (D) unit 246, and D cache 248. Functionality of one or moreof the various components may be implemented as fixed function units orthrough the use of code implemented on programmable processing units.The BCI unit 220 receives data and commands from a bus interface unit,such as BIU 118 (FIG. 1), and responsively initializes the processing ofthe vertex data. The P units 236 and 238, and ZL1 cache 230 and D cache248, respectively, interface (perform read and write operations) with amemory interface unit, such as MIU 110, as well as the BIU 118. Notethat the P units 236 and 238 may be physically embodied in the Z cache234 and T cache 242, respectively, in some embodiments. The P units 236and 238 (also referred to herein individually or collectively as packetlogic) comprise an embodiment of the packet processing system 100 a, asdelineated by the dotted line, although fewer or greater components maybe included in some embodiments of a packet processing system 100. Forinstance, the packet processing system 100 a may further comprise driversoftware 150 that is configured to control processing of the P units 236and 238, and/or a core processor (e.g., engine), or may be embodied asthe entire graphics processing unit 114 or graphics processor system 10in some embodiments.

FIG. 2B comprises a functional block diagram that illustrates oneembodiment of the packet processing system 100. As shown, the packetprocessing system 100 comprises a segregator 260, receiver 268, writinglogic 266, and driver software 150. The segregator 260 further comprisesmasking logic 262 and swapping logic 264. The segregator 260 isconfigured to segregate an entire packet into two contiguous groups, afirst group comprising a first type of data and a second groupcomprising a second type of data. The receiver 268 is configured toreceive data over a PCIE connection (e.g., from BIU 118). The writinglogic 266 is configured to write data to a cache (e.g., Z cache 234,T-cache 242). The driver software 150 is configured to coordinate andcontrol functionality of the receiver 268 and the segregator 260. Oneskilled in the art would appreciate in the context of this disclosurethat one or more of the various logic (e.g., 260, 268, 266, etc.) of thepacket processing system 100 may be duplicated for each packet unit 236and 238 or shared in some embodiments.

Referring to FIGS. 2A and 2B, in one embodiment, the P units 236 and 238comprise logic gates, including registers, configured to enable mask(masking logic 262) and byte swapping (swapping logic 264)functionality, among other functionality such as edge calculations. TheZL2 unit 232 and the ZL3 unit 244 access the Z cache 234. The D unit 246is coupled to the PS 240 and ZL3 unit 244, and is responsible for colorfunctionality, as is known, and further accesses the D cache 248. The PS240 accesses the T cache 242, which corresponds to texture processingaccording to well-known mechanisms. Note that functionality of one ormore components shown in FIGS. 2A and 2B may be combined in a singlecomponent in some embodiments, or functionality of a single componentmay be distributed among two or more components.

In operation, the BCI 220 receives a command from the driver software150 or other software to draw a triangle or other primitive. The BCI 220also receives vertex information corresponding to the triangle to bedrawn. The vertex information is passed to the VS 222, where vertextransformations are implemented. The VS 222 may comprise shaderprogramming or code executed on a programmable unit (e.g., coreprocessor or engine in the GPU 114). In some embodiments, the VS 222 maybe implemented as a fixed function unit. In particular, objects aretransformed from object space to work space and screen space astriangles. The triangles are passed to the TSU 224, which assemblesprimitives, and also performs well-known tasks such as bounding boxgeneration, culling, edge function generation, and triangle levelrejections, among other well-known functions. The TSU 224 passes data tothe STG unit 226, which provides tile generation functionality, wherebythe data objects are segmented into tiles (e.g., 8×8, 16×16, etc.) andpassed to the ZL1 unit 228.

The ZL1 unit 228, like the ZL2 and ZL3 units 232, 244, respectively,performs z-value processing, such as high-level rejection of z-values(e.g., where fewer bits are consumed than similar processing at a lowerlevel). The ZL units 228, 232, and 244 operate in conjunction with theZL1 cache 230, Z cache 234, and Z cache 234, respectively. The PS 240may comprise shader programming executed on a programmable unit (e.g.,core processor or engine in the GPU 114) that receives texture andpipelined data and provides outputs to the D unit 246 and ZL3 unit 244.In some embodiments, the PS 240 may comprise a fixed function unit. TheD unit 246 and ZL3 unit 244 are configured to perform alpha testing andstencil testing before values in the Z cache 234 or D cache 248 need tobe updated.

The P units 236 and 238 process packets (e.g., perform segregate andswap functionality, as explained below) corresponding to the z-data ands-data cached in the Z cache 234 and T cache 242, respectively. Forinstance, a host application may request processing of a surface derivedfrom only z-data (to the exclusion of s-data). The host applicationrequest is implemented through the driver software 150 communicated tothe GPU 114 via the BIU 118. The driver software 150 programs registersin the GPU 114 and instructs a core processor (e.g., engine) in the GPU114 to enable this z-only format. In response to the instructionsconveyed by the driver software 150 on behalf of the host application,the core processor generates a mask and stores in one or more registersaccessible to the P units 236 and 238 to enable the P units 236 and/or238 to perform the segregate and swap functionality before outputtingthe required packet format (i.e., z-only) via the BIU 118 or MIU 110.For instance, the P unit 238, in response to a read request to the BIU118, receives data from the BIU 118 in a pre-processing packing format(see FIG. 3, the packet labeled as 300). The address of the packetcorresponding to reading (or writing) operations may be generated by thecore processing unit (e.g., engine) in the GPU 114. Referring to FIG. 3,the packet 300 comprises two different types of data comprising stencil(s) data 303 and depth or z-data 305. In this exemplary implementation,three contiguous bytes (each block in FIGS. 3 and 4 holding a z or sdata represent a byte) of z-data 305 (e.g., z₀, z₀, z₀) are paired witha single stencil (s) data 303 (e.g., s₀). The P unit 238 imposes a maskoperation on the entire packet body using byte mask 302, and swaps thedata to form a pixel packet 400 having a post-processing packing formatcomprising two separate and contiguous groups 402 (z-data) and 404(s-data) as shown in FIG. 4. The P unit 238 writes one of the groups 402or 404 to the T cache 242. Note that the P unit 238 may write both s andz-data to the T-cache 242, but in one embodiment, the write occurs in amixed format (e.g., packet 300) as shown in FIG. 3.

With regard to the P unit 236, data in the Z cache 234 is formatted in apre-processing packing format as shown by packet 300 in FIG. 3. Forexample, in response to a write request to the BIU 118, the packet 300stored in the Z cache 234 has a mask operation (e.g., logic operation)imposed upon it by the P unit 236, and the data of the packet is swappedby the P unit 236. The result of the above-described mask and swapoperation is that the data is formatted to pixel packet 400 comprising apost-processing packing format as shown in FIG. 4. Various stages,labeled A and B in FIG. 2, are described below in association with FIGS.3-4.

Referring to FIG. 3, shown is the exemplary packet 300. The packet 300represents a packet in the stage designated as “A” in FIG. 2A(pre-processing packing format). As described above, a repetitivepattern comprising a combination of at least two different types of data(e.g., three contiguous bytes of z-data 305 (e.g., z₀, z₀, z₀) pairedwith a single byte of stencil (s) data 303 (e.g., s₀)) comprise thepacket 300. In operation, if the z-data 305 is the only data to bewritten (i.e., to the exclusion of the s-data 303), the P unit 236 (or Punit 238, with the P unit 236 discussed hereinafter for brevity with theunderstanding that similar application applies to the P unit 238)performs a byte-enable operation on the entire packet body 300. That is,the P unit 236 imposes a byte mask 302 on the entire packet 300, thebyte mask 302 having a bit pattern as shown that disables the s-data 303and enables the z-data 305. Thus, the byte mask 302 imposed by the Punit 236 comprises the data pattern 11101110 . . . 1110. That is, the Punit 236 imposes a zero (0) value every 4 bits, with the 0-bit valuerepresenting disabling functionality (i.e., causing the masked bit toretain its value). The bit value of one (1) represents enablingfunctionality, or rather, allows that masked bit to be passed. Oneskilled in the art would understand in the context of this disclosurethat the mask bit value and associated functionality can be reversed torepresent disabling and enabling functionality in some embodiments(e.g., “1” to disable, “0” to enable).

Note that if it is desired to write s-data 303 (to the exclusion of thez-data 305), then the pattern would comprise an inversion of the bitpattern as shown by byte mask 304, namely, 00010001 . . . 0001. Further,if it is desired that all bits are passed, then the mask bit patternwould comprise all ones (1s) (not shown). Thus, the P units 236 (and238) imposes a byte mask 302 that provides for selective writes of thecombined and contiguous bytes of the packet body 300.

FIG. 4 represents a pixel packet 400 in the stage designated as “B” inFIG. 2A, and shows a post-processing packing format that comprises twocontiguous groups of z-data 402 and s-data 404. The pixel packet 400 maybe written to local memory 106 via MIU 110 or to the BIU 118 (or one ofthe groups 402 or 404 may be written to the T cache 242 by P unit 238 inresponse to a read request to the BIU 118, or both s and z-data may bewritten to the T cache 242 in mixed format as explained above). Asshown, the z-data group 402 and s-data group 404 are segregated fromeach other to enable select writes of contiguous chunks (bits or bytes)of data. In one embodiment, all of the z-data of group 402 is moved(e.g., swapped) to the first packet portion (e.g., first 48 bytes), andall of the s-data of group 404 is moved to the last packet portion(e.g., the last 16 bytes). For example, 16 bytes may be designated forthe s-data group 404, which are retained based on the “0” mask bitvalues. The 48 bytes corresponding to the “1” mask bit values describedin FIG. 2A enable the write of z-data group 402 only (to the exclusionof the s-data group 404). If the s-data group 404 is desired to bewritten, similar processing may be applied with the “1” mask bit valuesapplied to the zero values.

FIG. 5 is a flow diagram that illustrates a packet processing method 100b embodiment that may be implemented under the control of driversoftware 150 in cooperation with the P units 236 and/or 238. One methodembodiment, among others, comprises receiving a packet having at least afirst type of data and a second type of data over a PCIE connection(502), and segregating the entire packet into two contiguous groups, afirst group comprising the first type of data and a second groupcomprising the second type of data (504).

Any process descriptions or blocks in the flow diagram shown in FIG. 5should be understood as representing modules, segments, or portions ofcode which include one or more executable instructions for implementingspecific logical functions in the process, and alternate implementationsare included within the scope of the disclosed embodiments in whichfunctions may be executed out of order from that shown or discussed,including substantially concurrently or in reverse order, depending onthe functionality involved, as would be understood by those reasonablyskilled in the art of the present invention.

It should be emphasized that the above-described embodiments of thedisclosure, particularly, any “preferred” embodiments, are merelypossible examples of implementations, merely set forth for a clearunderstanding of the principles of the packet processing systems andmethods. Many variations and modifications may be made to theabove-described embodiment(s) without departing substantially from thespirit and principles of the invention. All such modifications andvariations are intended to be included herein within the scope of thisdisclosure and protected by the following claims.

1. A packet processing system in a peripheral componentinterconnect-express (PCIE) compliant system, comprising: a receiver forreceiving a packet having at least a first type of data and a secondtype of data over a PCIE connection; a segregator for segregating theentire packet into two contiguous groups, a first group comprising thefirst type of data and a second group comprising the second type ofdata; masking logic configured to mask the first type of data and thesecond type of data; swapping logic configured to swan the first type ofdata and the second type of data according to the mask result of themasking logic; and a writing logic for writing one of the two contiguousgroups to the exclusion of the other contiguous group.
 2. The system ofclaim 1, wherein the writing logic is further configured to write one ofthe two contiguous groups to a memory through a memory interface unit.3. The system of claim 1, wherein the writing logic is furtherconfigured to write one of the two contiguous groups to a bus interfaceunit coupled to one or a combination of a system memory, a hostprocessor, and a chipset.
 4. The system of claim 1, wherein the writinglogic is further configured to write at least a contiguous byte ofstencil data, a contiguous byte of z-data, or both.
 5. The system ofclaim 1, wherein the writing logic is further configured to write atleast a contiguous byte of color data, a contiguous byte of alpha data,or both.
 6. The system of claim 5, wherein the masking logic is furtherconfigured to generate one or a combination of enabling and disablingmask bits and impose the mask bits on the z data and the stencil data.7. The system of claim 1, further comprising driver software configuredto coordinate and control functionality of the receiver and thesegregator.
 8. A method for processing a packet in a peripheralcomponent interconnect-express compliant (PCIE) system, comprising:receiving a packet having at least a first type of data and a secondtype of data over a PCIE connection; segregating the entire packet intotwo contiguous groups according to a mask having a bit pattern forenabling the two contiguous groups, a first group comprising the firsttype of data and a second group comprising the second type of andwriting one of the two contiguous groups to the exclusion of the othercontiguous group.
 9. The method of claim 8, wherein writing compriseswriting one of the two contiguous groups to a memory through a memoryinterface unit.
 10. The method of claim 8, wherein writing compriseswriting one of the two contiguous groups to a bus interface unit coupledto one or a combination of a system memory, a host processor, and achipset.
 11. The method of claim 8, wherein writing comprises writing atleast a contiguous byte of stencil data, a contiguous byte of z-data, orboth.
 12. The method of claim 8, wherein writing comprises writing atleast a contiguous byte of color data, a contiguous byte of alpha data,or both.
 13. The method of claim 8, wherein segregating comprisesswapping the first type of data and the second type of data.
 14. Themethod of claim 8, wherein segregating comprises masking the first typeof data and the second type of data.
 15. The method of claim 14, whereinmasking comprises generating one or a combination of enabling anddisabling mask bits and imposing the mask bits on the z data and thestencil data.
 16. The method of claim 8, further comprising coordinatingand controlling receiving and segregating.
 17. A graphics processorsystem, comprising: a peripheral component interconnect-express (PCIE)connection; and a graphics processing unit coupled to the PCIEconnection, the graphics processing unit comprising packet logicconfigured to receive a packet having at least two types of data overthe PCIE connection and separate the entire packet into two contiguousgroups, a first group comprising a first type of data and a second groupcomprising a second type of data; wherein packet logic is furtherconfigured to separate the entire packet by writing one of the two typesof data to the exclusion of the other type of data according to a bytemask that provides for selective write of the two contiguous groups. 18.The graphics processor system of claim 17, wherein the first type ofdata comprise z-data and the second type of data comprises stencil data.19. The graphics processor system of claim 17, wherein the first type ofdata comprise color data and the second type of data comprises alphadata.
 20. The graphics processor system of claim 17, further comprisingdriver software configured to provide the packet to the graphicsprocessing unit over the PCIE connection.